ISO stands for International Organization for Standardization adopted by many countries, here is a description. So if getting a chip, why not use one that is recognized almost everywhere.

All EU countries as well as many other countries require that your pet have a microchip that meets ISO Standards 11784/11785. Due to new regulations promulgated in 2006, the ISO microchip became the standard for all of Europe. If your pet is ever separated from you while traveling in Europe, the shelters and veterinarians can only read this chip. More than 20 other countries also require that your pet carry a microchip that meets the ISO standards.

I doubt Abby girl will ever leave Oklahoma let alone the US. The main reason we want to chip ASAP is tornado season is breathing down our throats and with what happened last year here we want to be prepared.